1. Field of the Invention
The present invention relates to laser machining, and in particular to laser machining method and apparatus in which a gap amount between a machining nozzle and a workpiece is maintained to be a constant value in machining.
2. Description of Related Art
There is known a laser machining method in which a machining head is moved relative to a workpiece along a predetermined machining shape while controlling a gap amount between the machining nozzle and the workpiece to be maintained to a reference value in machining. This machining method is known as laser machining with a gap control or a tracing control. In machining a plurality of separate machining shapes on a workpiece by such laser machining method, there has been adopted a process in which the gap control is discontinued at a machining end point of one machining shape and the machining head is moved away from the workpiece and then moved to a start position of a next machining shape where the gap control is continued for the next machining shape, so as to evade a possible obstacle such as a distortion of the workpiece or a dross caused by the laser machining and a cut piece suspended at the machining position.
FIG. 1 shows a conventional control method in a transition from machining of one machining shape to machining of a next machining shape.
For starting a laser machining (cutting) operation for a next machining shape S2 after completing a laser machining operation of one machining shape S1, when a machining nozzle reaches a machining end point A, the machining nozzle is moved away from the workpiece in a Z-axis positive direction by driving a Z-axis by rapid traverse by a predetermined amount to be stop at a point B, and then the machining nozzle is moved to a machining start point D of a next machining shape S2 by rapid traverse by driving X- and Y-axes. After the machining nozzle reaches the point D, the machining nozzle is moved in the Z-axis negative direction at an approach feed velocity to a point E where a gap amount is a predetermined value to start the machining of the next machining shape S2 with the gap control.
In the above method of moving the machining head for evading a possible obstacle in a motion path from a machining end point of one machining shape to a machining start point of the next machining shape, a length of the motion path of the machining head is elongated since the machining head is moved along a rectangular path, and it takes a long time for the machining head from the machining end point to the machining start point even if the machining head is moved by rapid traverse since the driving of axis is switched from the Z-axis to the X- and Y-axes and then changed to the Z-axis and the motion of the machining head is stopped each time of changing the driving of the axis, to affect machining time to cause lowering of machining efficiency.